A common wooden building is constructed such that temperature inside an attic thereof is rendered similar to the temperature of outside air as much as possible by providing an attic ventilating opening in a region such as the transverse wall thereof, and so forth, however, the temperature inside the attic rises at times to a high level (70° C. or higher) depending on a building district where the building is built, insolation condition, and a season involved.
In order to mitigate such adverse effect of heating in the space of the attic on a sitting room, it is a common practice to install a fibrous heat insulator for blowing or a rigid urethane foam heat insulator on the rear face of the ceiling of the sitting room.
In FIG. 8, a rigid urethane foam heat insulator 2 installed on the upper face of the ceiling of a conventional sitting room is shown, and the rigid urethane foam heat insulator 2 having a thickness of 200 mm is laid on the ceiling 3 while a ventilating opening O2 is provided in the upper part of the outside wall W.
Accordingly, heat transfer in the interior Ro of the attic takes place such that intruding heat T1 propagating through the surface of the roof 4 and gaps O1 heats up the rigid urethane foam heat insulator 2 to be accumulated therein while warms up the interior Ro of the attic, part of the intruding heat propagates into the sitting room R as transmission heat T3, and hot air having heated up the rigid urethane foam heat insulator 2 is emitted through the ventilating opening O2 as emission heat T2, thereby forming a circulatory flow of the intruding heat T1.
Even a heat insulator having high heat insulating performance such as a rigid urethane foam heat insulator 2 and a fibrous heat insulating member 2 for blowing will reach a high temperature after absorbing heat, and, if subjected to heating by solar heat for long hours, whereupon the transmission heat T3 at a high temperature is conducted by transmission to a sitting room R, thereby interfering with maintenance of a comfortable environment in the sitting room R, that is, maintenance of an adequate room temperature. In addition, even if the temperature of the outside air T1 falls, the heat insulator 2 acting as a heat accumulator cools down slowly owing to its heat capacity, so that the heat insulator 2 acting to insulate heat at a high temperature in the interior Ro of the attic during the day emits heat acting as the heat accumulator at night, thereby causing a problem that air conditioning equipment in the room R, such as a cooler, will be subjected to an untoward load.
The invention has been developed to overcome the problem described above, and it is an object of the invention to mitigate heat accumulation in the heat insulator 2 by protecting the heat insulator 2 with a heat shielding member 1 so as not to allow heat of air at temperature during the day to directly heat the heat insulator 2 to be accumulated therein, and by blocking and reducing a heating load applied to the heat insulator 2 by the agency of the heat shielding member 1. Accordingly, the invention is quite effective when applied to a heat insulator installed on the rear surfaces of the roof and the ceiling, respectively, subjected to a strong effect of radiant heat (heat rays), and a heat insulator installed on the rear surfaces of the outside wall, the floor, and so forth, under the influence of radiant heat.